Objective: This study investigated the effectiveness of the Positivity & Rules Program (PR program), a behavioral teacher program targeting ADHD symptoms in the classroom involving both student-focused and classroom-focused programs. Method: Primary school children with ADHD symptoms (N = 114) were randomly assigned to the PR program (n = 58) or control group (n = 56). Teacher and parent ratings were used to assess behavioral, social, and emotional functioning at baseline, during and after the intervention. Intervention effects were assessed using intention-to-treat multilevel analyses. Results: Teachers reported positive effects on ADHD symptoms and social skills (.01 < f² > .36). Effects did not generalize to the home setting. Conclusion: The PR program holds promise for improving classroom behavior in children with ADHD symptoms and might prevent escalation of problem behavior